For example, background-art techniques in this technical field include International Publication WO 2013/002054 Pamphlet (Patent Literature 1). In the Pamphlet, there has been described a solar heat collection system which is provided with a low-temperature heating device, a steam-water separation device, a high-temperature heating device, and a circulating pump (see Abstract). The low-temperature heating device heats water supplied from a feedwater pump by use of sunlight heat. The steam-water separation device separates a water-steam two-phase fluid generated by the low-temperature heating device into water and steam. The high-temperature heating device heats the steam separated by the steam-water separation device by use of the sunlight heat. The circulating pump supplies the water separated by the steam-water separation device to the low-temperature heating device.